Sharma, Anu

Type 2 diabetes mellitus is a polygenic disease with a variable phenotype. Many genetic associations have been described; however, understanding their underlying pathophysiological role in Type 2 diabetes mellitus is important for development of future therapeutic targets. Here, we review the physiological mechanisms of diabetes-associated variants that affect glycemia.

Context: Prediabetes is a heterogeneous disorder classified on the basis of fasting glucose concentrations and 2-hour glucose tolerance. Objective: We sought to determine the relative contributions of insulin secretion and action to the pathogenesis of isolated impaired glucose tolerance (IGT). Design: The study consisted of an oral glucose tolerance test and a euglycemic clamp performed in two cohorts matched for anthropometric characteristics and fasting glucose but discordant for glucose tolerance. Setting: An inpatient clinical research unit at an academic medical center. Patients or Other Participants: Twenty-five subjects who had normal fasting glucose (NFG) and normal glucose tolerance (NGT) and 19 NFG/IGT subjects participated in this study. Intervention(s): Subjects underwent a seven-sample oral glucose tolerance test and a 4-hour euglycemic, hyperinsulinemic clamp on separate occasions. Glucose turnover during the clamp was measured using tracers, and endogenous hormone secretion was inhibited by somatostatin. Main Outcome Measures: We sought to determine whether hepatic glucose metabolism, specifically the contribution of gluconeogenesis to endogenous glucose production, differed between subjects with NFG/NGT and those with NFG/IGT. Results: Endogenous glucose production did not differ between groups before or during the clamp. Insulin-stimulated glucose disappearance was lower in NFG/IGT (24.6 ± 2.2 vs 35.0 ± 3.6 μmol/kg/min; P = .03). The disposition index was decreased in NFG/IGT (681 ± 102 vs 2231 ± 413 × 10−14 dL/kg/min2 per pmol/L; P < .001). Conclusions: We conclude that innate defects in the regulation of glycogenolysis and gluconeogenesis do not contribute to NFG/IGT. However, insulin-stimulated glucose disposal is impaired, exacerbating defects in β-cell function.

Background: Thyroid lymphoma is a relatively rare disease often posing a diagnostic challenge. Reaching the final diagnosis can be delayed if insufficient biopsy material is obtained for immunohistochemistry analysis. The aim of this study was to evaluate the clinical, biochemical, and radiological features of thyroid lymphoma. Methods: A retrospective analysis was conducted of all Mayo Clinic patients evaluated between 2000 and 2014 who had a tissue biopsy positive for thyroid lymphoma. Results: Seventy-five subjects had biopsy-proven thyroid lymphoma, and 62.7% were primary thyroid lymphomas. The median age at diagnosis was 67 years (range 20–90 years). A total of 50.7% were male, and 54.7% had a history of Hashimoto's thyroiditis. Presenting symptoms included neck mass (88%), dysphagia (45.3%), and hoarseness (37.3%). The typical ultrasound appearance consisted of a solid, hypoechoic mass with increased vascularity and variable edge characteristics. Fine-needle aspiration (FNA) biopsies were abnormal in 70.7% of cases, and 42% indicated a specific lymphoma subtype. The diagnosis was confirmed in 53.3% by core biopsy, in 21.3% by thyroidectomy (partial or total), in 12% through incisional biopsy, and in 12% by lymph node biopsy. Core biopsy had a higher sensitivity compared with FNA (93% vs. 71%, p = 0.006). Conclusion: A rapidly enlarging neck mass in the setting of Hashimoto's thyroiditis should raise suspicion for thyroid lymphoma. Radiologically, this usually presents as a large, unilateral, thyroid-centered mass, hypoechoic by ultrasound, and expanding into adjacent soft tissues. Core-needle biopsy should be the first diagnostic test to expedite reaching the final diagnosis and decrease patient burden of additional tests and interventions.